1. Field of the Invention
The present invention relates to a key system, and more particularly, to a key system utilizing two operation nodes to detect a status of a plurality of keys.
2. Description of the Prior Art
Monitors generally provide keys for users to adjust brightness, contrast, and color of the monitors. The keys are controlled by a microcontroller. In the prior art, the keys can be divided into an analog key system and a digital key system. The analog key system utilizes one I/O pin of the microcontroller to control multiple keys and determines which key is activated by a voltage divider. The digital key system controls one key with one I/O pin of the microcontroller directly.
Please refer to FIG. 1. FIG. 1 is a diagram of an analog key system 10 according to the prior art. The analog key system 10 includes six resistors 11-16 connected in series, and six keys 21-26. One end of the six resistors 11-16 connected in series is connected to a power supply VCC, and another end of the six resistors 11-16 is connected to a ground GND. One end of the six keys 21-26 connects to one end of the six resistors 11-16 respectively, and the other ends of the six keys 21-26 all connect to one I/O pin of a microcontroller 20. The I/O pin of the microcontroller 20 can read the divided voltage of the six resistors 11-16 connected in series to determine which one of the six keys 21-26 is activated.
Please refer to FIG. 2. FIG. 2 is a diagram of a digital key system 30 according to the prior art. The digital key system 30 includes six keys 31-36 and a resistor 37. One end of the resistor 37 is connected to a power supply VCC, and another end of the resistor 37 is connected to a ground GND. One end of the six keys 31-36 connects to the ground GND, and another end of the six keys 31-36 connects to six I/O pins of a microcontroller 38 respectively. Thus, when one of the six key 31-36 is activated, the microcontroller 38 can read the ground voltage from the I/O pins correspondingly.
Keys will oxidize after a period of time, which results in contact fault. The analog key system, which determines which key is activated through voltage division requires high sensitivity; otherwise, it is easy to misjudge which key is activated. The digital key system uses one I/O pin of the microcontroller for each key, which does not make efficient use of the microcontroller pins.